Airless Dispensing Packages

By Victor Suben, P. E.

Most cosmetic and skin care products contain preservatives to prevent the growth of microbes that might cause con­­sumers to experience allergic or other adverse reactions. In some cases, the preservativescan cause skin irritation.

It has long been thought that an airless, or anaerobic, packaging system would permit manufacturers to discontinue the use of preservatives, while at the same time preventing the growth of aerobic microbes. To this end, an entire class of airless dispensing systems has been developed.

A Little Background

Some knowledge of traditional pump dispensers is key in understanding airless dispensing systems. Most common pump dispensers are basically comprised of a dip tube, a pump body, or tank, a piston, a stainless steel spring, and an actuator placed inside a rigid container. In addition, there may be one or two check balls to prevent liquid from flowing out of the pump body back into the container, and from flowing back into the pump body from the piston and actuator. When the actuator is de­pressed to dispense the product, the pressure in the tank is increased, causing liquid to flow through orifices in the piston and out through the orifice in the actuator. At the same time the actuator is depressed, the stainless steel spring is compressed. When the actuator is released, the spring provides the force to restore the actuator to its original position.

As the actuator and piston move up toward their original positions, a slight vacuum is created in the pump body, which allows the check ball to lift up off its seat, and allows another dose of liquid to fill the pump body. Simultan­eously, as the actuator and piston move up, channels are opened that allow outside air to enter the container. This air replaces the volume of liquid drawn into the pump body, thereby preventing the build up of a partial vacuum that would prevent further dispensing from a rigid container. Obviously, traditional pump dispensers are not anaerobic— that is, the product is always in contact with air.

Airless Systems

In so-called airless systems, the product is isolated from the air. In addition, the dosage expelled with each stroke of the actuator is approximately equal to the amount of product contained in the pump body. Thus, this is not a system that will dispense continuously while the actuator is held in the down position.

There are several forms of airless systems. However, in this context it is important to note that by the term airless, we mean that the product is separated from the surrounding air by a barrier that prevents its ingress.

Aerosols Are Airless

Probably the most ubiquitous airless package is the aerosol. After filling with the concentrate, the aerosol can is subjected to a partial vacuum, normally in the range of 18 to 22 inches of mercury (61—74 kPa). While still under this partial vacuum, the mounting cup with the aerosol valve is crimped onto the can. The propellant, usually amixture of iso-butane and propane, is added either under the cup or through the valve.

Basically, there is a flow-in gasket between the mounting cup and the container. The stem gasket provides a seal to prevent product dispensing until the actuator is de­pressed. When the actuator is depressed, the valve stem moves downward, compressing the return spring and also moving the orifice in the stem below the valve stem gasket. This enables the product to flow up the dip tube, through the valve and the orifice in the actuator, to the atmosphere. Unlike mechanical pump dispensers, aerosol systems will continue to dispense as long as the actuator is depressed.

Mechanical Pump Dispensers

Other airless systems use more common and environmentally friendly mechanical pump dispensers. These types of dispensers take several different forms.

Exxel Container Inc., Somerset, NJ, has developed the Atmos system that dispenses product like an aerosol with one major difference. The Exxel package does not use a chemical propellant.

Before filling, the Exxel system is comprised of a thin wall PET bottle that is folded in a particular pattern. This bottle is placed inside a natural rubber sleeve, which in turn is placed inside and sealed to an outer, rigid container. When product is filled into the PET bottle, it expands, stretching the rubber sleeve. Once the bottle is filled, the actuator and valve are hermetically sealed to it, and the system is ready for operation. When the actuator is depressed, it opens the valve, and the pressure induced by the stretched rubber sleeve (similar to a stretched rubber band returning to its original size once the stretching force is removed) causes product to be dispensed. Product will continue to be dispensed as long as the actuator is depressed.

In my experience, the Exxel system is able to dispense about 80% to 85% of its contents before the sleeve re­turns to its original (un-stretched) size. For companies with a policy that requires that a customer be able to get at least the amount of product stated on the label, the package must be overfilled by the amount of residual product in the package.

Use of Flexible Pouches

Most of the earliest forms of airless containers were comprised of flexible pouches affixed to mechanical pump dispensers contained in rigid outer containers. Some of these systems had dip tubes through which product flowed into the pump body, and others did not.Each manufacturer has its own proprietary system for attaching the pouch to the pump body, and the entire assembly to the outer rigid container. The pouches themselves are often comprised of several layers to provide a barrier against moisture and air.

Operation of such systems is similar to the operation of ordinary mechanical pump dispensers. The difference with the pouch system is that the air required to fill the void left by the dispensed product is directed into the space between the inner wall of the rigid container and the outer surface of the flexible pouch. This enables the pouch to collapse thereby keeping the product in contact with either the dip tube’s inlet, or the inlet to the pump body. Such systems were able to dispense about 90+% of the product. How­ever, there were some instances of leakage when the connection between the pouch and the pump either failed during use or as a result of a manufacturing flaw.

French System Dispenses More

Lablabo, a French company represented in the U.S. by SGB Pack­aging Group, Hacken­sack, NJ, introduced an interesting airless system. The company supplies an inner container within an outer container. The pump dispenser is supplied separately. In operation, the inner container is filled with product, and the pump is snapped in place. As the pump is operated and product dispensed, the inner container collapses. In tests of this system, we were able to dispense between 95% to 98% of the product.

PBM Offers a Variation

PBM Plastics, Newport News, VA, has anew airless system that is slightly different from Lablabo’s. This system utilizes a collapsible liner that is placed inside a rigid, outer container. The product is dispensed through a lotion or a spray pump, creating a vacuum inside the liner that causes it to collapse thereby keeping the product in contact with the pump inlet.

PBM Plastics states that the liners are formed during the melt-phase. This eliminates molded-in stresses and helps ensure the integrity of the liner and overall system. The liner’s stiff upper rim serves a dual purpose, securing the liner within the bottle and providing a gasket to eliminate leaking.

The liner technology can dispense product, according to PBM, even when it is inverted because, as the liner collapses around the product, it creates a positive pressure on the contents that enables it to be easily dispensed. As a further benefit, the outer bottle and pump dispenser can be re-used. Once it is emptied, the collapsed liner easily be replaced with a new one. When the pump dispenser is re-secured in place, the package is ready for use. The liner is equipped with a metal collar and pull-tab type cover to provide security during shipping and storage. Once placed in the outer container, the cover is removed, and the pump re-secured in place.

Consumers would probably find the PBM system economical because it can be refilled. Also, this system seems to be environmentally friendly by virtue of the fact that only the liner needs to be discarded when the product has been exhausted. Both this and the Lablabo systems have the potential to produce the outer container in any shape without sacrificing the ability to dispense nearly all the product. Also, as can be seen in the picture on page 28,pumps with or without dip tubes can be used in these packages.

Unlike the Exxel system, neither the Lablabo, nor the PBM Plastics systems can dispense product in a continuous stream. Instead, the product is dispensed in discrete doses corresponding to the size of the pump body. However, also unlike the Exxel’s Atmos system, both of the latter two systems require less over-filling in order to dispense enough product to meet the label claim. Thus an economic assessment should be made to compare the cost of the Atmos package with the cost of the other two. If the costs are close, then the decision as to which to use could be based upon the amount of product to be filled, and the cost of the product.

For more information: Exxel: (732) 560-3655; for Lablabo, SGB Pack­aging Group Inc.: (201) 488-3030; PBM Plas­tics, (757)-888-6800.